* {
    margin: 0;
    padding: 0;
}
.div1 {
    width: 200px;
    height: 200px;
    background-color: green;
    /* margin-bottom: 10px; */
    /* 上右下左 */
    margin: 10px 20px 30px;
    /* 边框 */
    border-top: 20px solid red;
    border-right: 20px solid black;
    border-bottom: 20px solid red;
    border-left: 20px solid black;
}
.div2 {
    width: 500px;
    height: 200px;
    background-color: pink;
}
.div3 {
    width: 0px;
    height: 0px;
    /* background-color: pink; */
    margin: 50px;
    padding: 10px;
    /* 边框：边框宽度 线型 颜色 */
    border-top: 60px solid transparent;
    border-right: 60px solid transparent;
    border-bottom: 60px solid red;
    border-left: 60px solid transparent;
}
.div4 {
    width: 100px;
    height: 100px;
    /* background-color: rgba(0, 0, 0, .5); */
    background-color: #f00;
    opacity: .5;
    /* 边框圆角 */
    border-radius: 50%;
}
.div5 {
    width: 260px;
    height: 100px;
    background-color: red;
    border-radius: 50px;
}